In response to the needs of the transportation industry and the regulations governing the amount of time that a driver may spend behind the wheel, many vehicles include a cab compartment and a sleeper compartment where the driver or passenger can rest. To create a comfortable environment for drivers and passengers, vehicle heating, ventilation, and air conditioning (HVAC) systems have been developed to provide conditioned air to the cab and sleeper compartments.
Such vehicle HVAC systems may include multiple evaporators, one for each compartment. For example, a system may include a cab evaporator (e.g., an evaporator associated with the cab compartment to cool the cab compartment) and a sleeper evaporator (e.g., an evaporator associated with the sleeper compartment to cool the sleeper compartment). Such systems may also include multiple compressors connected to different power sources so that the vehicle HVAC systems can be operated when the engine of the vehicle is on and when it is off.
To meet a specific cooling demand and reduce waste of compressed and condensed refrigerant, the systems may be operated to allow the compressed and condensed refrigerant to pass through one or more of the evaporators while restricting the condensed refrigerant from passing through other evaporator(s). For example, in a case where cooling in the sleeper compartment is not desired (e.g., the sleeper compartment is not occupied), the systems may be operated to restrict the refrigerant from passing through the sleeper evaporator to reduce waste of the compressed and condensed refrigerant on an unoccupied compartment. Similarly, in a case where cooling in the cab compartment is not desired, the systems may be operated to restrict the refrigerant from passing through the cab compartment.
While restricting the refrigerant from passing through the non-operating evaporator or evaporators (e.g., the sleeper evaporator when cooling in the sleeper compartment is not desired or the cab evaporator where cooling in the cab compartment is not desired), conventional systems cannot prevent the collection or accumulation of the refrigerant in the non-operating evaporator(s), in particular at the lower pressure side of the non-operating evaporator(s). The collection or accumulation of the refrigerant in the non-operating evaporator(s) reduces the effective amount of the refrigerant that should be used to cool the compartment(s) in need of cooling, making it difficult to meet (in some circumstances, only partially meet) the cooling demand. Consequently, the cooling capacity and overall efficiency of the HVAC systems are reduced, and the operational costs are increased.
Given the above background, there is a need in the art for air conditioning systems with enhanced cooling efficiency and capacity that provide conditioned air to multiple compartments and that prevent undesired collection of refrigerant in non-operating evaporators.
The information disclosed in this Background section is provided for an understanding of the general background of the invention and is not an acknowledgement or suggestion that this information forms part of the prior art already known to a person skilled in the art.